1. Technical Field
The present invention relates to integrated circuit design and, more particularly, to chip authentication using scan chains having characteristic properties based on process variations.
2. Description of the Related Art
As electronic devices become increasingly interconnected, integrated circuits (ICs) are relied on more and more for performing security sensitive tasks, as well as for handling sensitive information. Therefore a need exists for ICs to be able to perform operations such as authentication, protection of confidential information, and secure communication in an inexpensive, yet highly secure way.
Existing solutions use on-chip ring oscillators as vehicles to authenticate ICs. Ring oscillators include an odd number of inversion delay circuit elements in a ring, such that a signal propagates continuously through the ring, switching an output with every cycle. Process variations cause variations in the delay length of each delay element, such that each ring oscillator will change its outputs at a unique output frequency that is randomly determined at the time of formation, which can be used as a signature or fingerprint for the IC. However, to increase the security level, additional ring oscillators are employed. These single-purpose ring oscillators substantially increase cost and circuit size and, as such, ring oscillator solutions do not scale well to contexts that demand high degrees of security.